/*
 * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.util.regex;

import java.util.Objects;

/**
 * An engine that performs match operations on a {@linkplain java.lang.CharSequence
 * character sequence} by interpreting a {@link Pattern}.
 *
 * <p> A matcher is created from a pattern by invoking the pattern's {@link
 * Pattern#matcher matcher} method.  Once created, a matcher can be used to
 * perform three different kinds of match operations:
 *
 * <ul>
 *
 * <li><p> The {@link #matches matches} method attempts to match the entire
 * input sequence against the pattern.  </p></li>
 *
 * <li><p> The {@link #lookingAt lookingAt} method attempts to match the
 * input sequence, starting at the beginning, against the pattern.  </p></li>
 *
 * <li><p> The {@link #find find} method scans the input sequence looking for
 * the next subsequence that matches the pattern.  </p></li>
 *
 * </ul>
 *
 * <p> Each of these methods returns a boolean indicating success or failure.
 * More information about a successful match can be obtained by querying the
 * state of the matcher.
 *
 * <p> A matcher finds matches in a subset of its input called the
 * <i>region</i>. By default, the region contains all of the matcher's input.
 * The region can be modified via the{@link #region region} method and queried
 * via the {@link #regionStart regionStart} and {@link #regionEnd regionEnd}
 * methods. The way that the region boundaries interact with some pattern
 * constructs can be changed. See {@link #useAnchoringBounds
 * useAnchoringBounds} and {@link #useTransparentBounds useTransparentBounds}
 * for more details.
 *
 * <p> This class also defines methods for replacing matched subsequences with
 * new strings whose contents can, if desired, be computed from the match
 * result.  The {@link #appendReplacement appendReplacement} and {@link
 * #appendTail appendTail} methods can be used in tandem in order to collect
 * the result into an existing string buffer, or the more convenient {@link
 * #replaceAll replaceAll} method can be used to create a string in which every
 * matching subsequence in the input sequence is replaced.
 *
 * <p> The explicit state of a matcher includes the start and end indices of
 * the most recent successful match.  It also includes the start and end
 * indices of the input subsequence captured by each <a
 * href="Pattern.html#cg">capturing group</a> in the pattern as well as a total
 * count of such subsequences.  As a convenience, methods are also provided for
 * returning these captured subsequences in string form.
 *
 * <p> The explicit state of a matcher is initially undefined; attempting to
 * query any part of it before a successful match will cause an {@link
 * IllegalStateException} to be thrown.  The explicit state of a matcher is
 * recomputed by every match operation.
 *
 * <p> The implicit state of a matcher includes the input character sequence as
 * well as the <i>append position</i>, which is initially zero and is updated
 * by the {@link #appendReplacement appendReplacement} method.
 *
 * <p> A matcher may be reset explicitly by invoking its {@link #reset()}
 * method or, if a new input sequence is desired, its {@link
 * #reset(java.lang.CharSequence) reset(CharSequence)} method.  Resetting a
 * matcher discards its explicit state information and sets the append position
 * to zero.
 *
 * <p> Instances of this class are not safe for use by multiple concurrent
 * threads. </p>
 *
 * @author Mike McCloskey
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @spec JSR-51
 * @since 1.4
 */

public final class Matcher implements MatchResult {

  /**
   * The Pattern object that created this Matcher.
   */
  Pattern parentPattern;

  /**
   * The storage used by groups. They may contain invalid values if
   * a group was skipped during the matching.
   */
  int[] groups;

  /**
   * The range within the sequence that is to be matched. Anchors
   * will match at these "hard" boundaries. Changing the region
   * changes these values.
   */
  int from, to;

  /**
   * Lookbehind uses this value to ensure that the subexpression
   * match ends at the point where the lookbehind was encountered.
   */
  int lookbehindTo;

  /**
   * The original string being matched.
   */
  CharSequence text;

  /**
   * Matcher state used by the last node. NOANCHOR is used when a
   * match does not have to consume all of the input. ENDANCHOR is
   * the mode used for matching all the input.
   */
  static final int ENDANCHOR = 1;
  static final int NOANCHOR = 0;
  int acceptMode = NOANCHOR;

  /**
   * The range of string that last matched the pattern. If the last
   * match failed then first is -1; last initially holds 0 then it
   * holds the index of the end of the last match (which is where the
   * next search starts).
   */
  int first = -1, last = 0;

  /**
   * The end index of what matched in the last match operation.
   */
  int oldLast = -1;

  /**
   * The index of the last position appended in a substitution.
   */
  int lastAppendPosition = 0;

  /**
   * Storage used by nodes to tell what repetition they are on in
   * a pattern, and where groups begin. The nodes themselves are stateless,
   * so they rely on this field to hold state during a match.
   */
  int[] locals;

  /**
   * Boolean indicating whether or not more input could change
   * the results of the last match.
   *
   * If hitEnd is true, and a match was found, then more input
   * might cause a different match to be found.
   * If hitEnd is true and a match was not found, then more
   * input could cause a match to be found.
   * If hitEnd is false and a match was found, then more input
   * will not change the match.
   * If hitEnd is false and a match was not found, then more
   * input will not cause a match to be found.
   */
  boolean hitEnd;

  /**
   * Boolean indicating whether or not more input could change
   * a positive match into a negative one.
   *
   * If requireEnd is true, and a match was found, then more
   * input could cause the match to be lost.
   * If requireEnd is false and a match was found, then more
   * input might change the match but the match won't be lost.
   * If a match was not found, then requireEnd has no meaning.
   */
  boolean requireEnd;

  /**
   * If transparentBounds is true then the boundaries of this
   * matcher's region are transparent to lookahead, lookbehind,
   * and boundary matching constructs that try to see beyond them.
   */
  boolean transparentBounds = false;

  /**
   * If anchoringBounds is true then the boundaries of this
   * matcher's region match anchors such as ^ and $.
   */
  boolean anchoringBounds = true;

  /**
   * No default constructor.
   */
  Matcher() {
  }

  /**
   * All matchers have the state used by Pattern during a match.
   */
  Matcher(Pattern parent, CharSequence text) {
    this.parentPattern = parent;
    this.text = text;

    // Allocate state storage
    int parentGroupCount = Math.max(parent.capturingGroupCount, 10);
    groups = new int[parentGroupCount * 2];
    locals = new int[parent.localCount];

    // Put fields into initial states
    reset();
  }

  /**
   * Returns the pattern that is interpreted by this matcher.
   *
   * @return The pattern for which this matcher was created
   */
  public Pattern pattern() {
    return parentPattern;
  }

  /**
   * Returns the match state of this matcher as a {@link MatchResult}.
   * The result is unaffected by subsequent operations performed upon this
   * matcher.
   *
   * @return a <code>MatchResult</code> with the state of this matcher
   * @since 1.5
   */
  public MatchResult toMatchResult() {
    Matcher result = new Matcher(this.parentPattern, text.toString());
    result.first = this.first;
    result.last = this.last;
    result.groups = this.groups.clone();
    return result;
  }

  /**
   * Changes the <tt>Pattern</tt> that this <tt>Matcher</tt> uses to
   * find matches with.
   *
   * <p> This method causes this matcher to lose information
   * about the groups of the last match that occurred. The
   * matcher's position in the input is maintained and its
   * last append position is unaffected.</p>
   *
   * @param newPattern The new pattern used by this matcher
   * @return This matcher
   * @throws IllegalArgumentException If newPattern is <tt>null</tt>
   * @since 1.5
   */
  public Matcher usePattern(Pattern newPattern) {
    if (newPattern == null) {
      throw new IllegalArgumentException("Pattern cannot be null");
    }
    parentPattern = newPattern;

    // Reallocate state storage
    int parentGroupCount = Math.max(newPattern.capturingGroupCount, 10);
    groups = new int[parentGroupCount * 2];
    locals = new int[newPattern.localCount];
    for (int i = 0; i < groups.length; i++) {
      groups[i] = -1;
    }
    for (int i = 0; i < locals.length; i++) {
      locals[i] = -1;
    }
    return this;
  }

  /**
   * Resets this matcher.
   *
   * <p> Resetting a matcher discards all of its explicit state information
   * and sets its append position to zero. The matcher's region is set to the
   * default region, which is its entire character sequence. The anchoring
   * and transparency of this matcher's region boundaries are unaffected.
   *
   * @return This matcher
   */
  public Matcher reset() {
    first = -1;
    last = 0;
    oldLast = -1;
    for (int i = 0; i < groups.length; i++) {
      groups[i] = -1;
    }
    for (int i = 0; i < locals.length; i++) {
      locals[i] = -1;
    }
    lastAppendPosition = 0;
    from = 0;
    to = getTextLength();
    return this;
  }

  /**
   * Resets this matcher with a new input sequence.
   *
   * <p> Resetting a matcher discards all of its explicit state information
   * and sets its append position to zero.  The matcher's region is set to
   * the default region, which is its entire character sequence.  The
   * anchoring and transparency of this matcher's region boundaries are
   * unaffected.
   *
   * @param input The new input character sequence
   * @return This matcher
   */
  public Matcher reset(CharSequence input) {
    text = input;
    return reset();
  }

  /**
   * Returns the start index of the previous match.
   *
   * @return The index of the first character matched
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   */
  public int start() {
    if (first < 0) {
      throw new IllegalStateException("No match available");
    }
    return first;
  }

  /**
   * Returns the start index of the subsequence captured by the given group
   * during the previous match operation.
   *
   * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
   * to right, starting at one.  Group zero denotes the entire pattern, so
   * the expression <i>m.</i><tt>start(0)</tt> is equivalent to
   * <i>m.</i><tt>start()</tt>.  </p>
   *
   * @param group The index of a capturing group in this matcher's pattern
   * @return The index of the first character captured by the group, or <tt>-1</tt> if the match was
   * successful but the group itself did not match anything
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IndexOutOfBoundsException If there is no capturing group in the pattern with the given
   * index
   */
  public int start(int group) {
    if (first < 0) {
      throw new IllegalStateException("No match available");
    }
    if (group < 0 || group > groupCount()) {
      throw new IndexOutOfBoundsException("No group " + group);
    }
    return groups[group * 2];
  }

  /**
   * Returns the start index of the subsequence captured by the given
   * <a href="Pattern.html#groupname">named-capturing group</a> during the
   * previous match operation.
   *
   * @param name The name of a named-capturing group in this matcher's pattern
   * @return The index of the first character captured by the group, or {@code -1} if the match was
   * successful but the group itself did not match anything
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IllegalArgumentException If there is no capturing group in the pattern with the given
   * name
   * @since 1.8
   */
  public int start(String name) {
    return groups[getMatchedGroupIndex(name) * 2];
  }

  /**
   * Returns the offset after the last character matched.
   *
   * @return The offset after the last character matched
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   */
  public int end() {
    if (first < 0) {
      throw new IllegalStateException("No match available");
    }
    return last;
  }

  /**
   * Returns the offset after the last character of the subsequence
   * captured by the given group during the previous match operation.
   *
   * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left
   * to right, starting at one.  Group zero denotes the entire pattern, so
   * the expression <i>m.</i><tt>end(0)</tt> is equivalent to
   * <i>m.</i><tt>end()</tt>.  </p>
   *
   * @param group The index of a capturing group in this matcher's pattern
   * @return The offset after the last character captured by the group, or <tt>-1</tt> if the match
   * was successful but the group itself did not match anything
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IndexOutOfBoundsException If there is no capturing group in the pattern with the given
   * index
   */
  public int end(int group) {
    if (first < 0) {
      throw new IllegalStateException("No match available");
    }
    if (group < 0 || group > groupCount()) {
      throw new IndexOutOfBoundsException("No group " + group);
    }
    return groups[group * 2 + 1];
  }

  /**
   * Returns the offset after the last character of the subsequence
   * captured by the given <a href="Pattern.html#groupname">named-capturing
   * group</a> during the previous match operation.
   *
   * @param name The name of a named-capturing group in this matcher's pattern
   * @return The offset after the last character captured by the group, or {@code -1} if the match
   * was successful but the group itself did not match anything
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IllegalArgumentException If there is no capturing group in the pattern with the given
   * name
   * @since 1.8
   */
  public int end(String name) {
    return groups[getMatchedGroupIndex(name) * 2 + 1];
  }

  /**
   * Returns the input subsequence matched by the previous match.
   *
   * <p> For a matcher <i>m</i> with input sequence <i>s</i>,
   * the expressions <i>m.</i><tt>group()</tt> and
   * <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(),</tt>&nbsp;<i>m.</i><tt>end())</tt>
   * are equivalent.  </p>
   *
   * <p> Note that some patterns, for example <tt>a*</tt>, match the empty
   * string.  This method will return the empty string when the pattern
   * successfully matches the empty string in the input.  </p>
   *
   * @return The (possibly empty) subsequence matched by the previous match, in string form
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   */
  public String group() {
    return group(0);
  }

  /**
   * Returns the input subsequence captured by the given group during the previous match operation.
   *
   * <p> For a matcher <i>m</i>, input sequence <i>s</i>, and group index <i>g</i>, the expressions
   * <i>m.</i><tt>group(</tt><i>g</i><tt>)</tt> and <i>s.</i><tt>substring(</tt><i>m.</i><tt>start(</tt><i>g</i><tt>),</tt>&nbsp;<i>m.</i><tt>end(</tt><i>g</i><tt>))</tt>
   * are equivalent.  </p>
   *
   * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left to right, starting at
   * one.  Group zero denotes the entire pattern, so the expression <tt>m.group(0)</tt> is
   * equivalent to <tt>m.group()</tt>. </p>
   *
   * <p> If the match was successful but the group specified failed to match any part of the input
   * sequence, then <tt>null</tt> is returned. Note that some groups, for example <tt>(a*)</tt>,
   * match the empty string. This method will return the empty string when such a group successfully
   * matches the empty string in the input.  </p>
   *
   * @param group The index of a capturing group in this matcher's pattern
   * @return The (possibly empty) subsequence captured by the group during the previous match, or
   * <tt>null</tt> if the group failed to match part of the input
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IndexOutOfBoundsException If there is no capturing group in the pattern with the given
   * index
   */
  public String group(int group) {
    if (first < 0) {
      throw new IllegalStateException("No match found");
    }
    if (group < 0 || group > groupCount()) {
      throw new IndexOutOfBoundsException("No group " + group);
    }
    if ((groups[group * 2] == -1) || (groups[group * 2 + 1] == -1)) {
      return null;
    }
    return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
  }

  /**
   * Returns the input subsequence captured by the given
   * <a href="Pattern.html#groupname">named-capturing group</a> during the previous
   * match operation.
   *
   * <p> If the match was successful but the group specified failed to match
   * any part of the input sequence, then <tt>null</tt> is returned. Note
   * that some groups, for example <tt>(a*)</tt>, match the empty string.
   * This method will return the empty string when such a group successfully
   * matches the empty string in the input.  </p>
   *
   * @param name The name of a named-capturing group in this matcher's pattern
   * @return The (possibly empty) subsequence captured by the named group during the previous match,
   * or <tt>null</tt> if the group failed to match part of the input
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IllegalArgumentException If there is no capturing group in the pattern with the given
   * name
   * @since 1.7
   */
  public String group(String name) {
    int group = getMatchedGroupIndex(name);
    if ((groups[group * 2] == -1) || (groups[group * 2 + 1] == -1)) {
      return null;
    }
    return getSubSequence(groups[group * 2], groups[group * 2 + 1]).toString();
  }

  /**
   * Returns the number of capturing groups in this matcher's pattern.
   *
   * <p> Group zero denotes the entire pattern by convention. It is not
   * included in this count.
   *
   * <p> Any non-negative integer smaller than or equal to the value
   * returned by this method is guaranteed to be a valid group index for
   * this matcher.  </p>
   *
   * @return The number of capturing groups in this matcher's pattern
   */
  public int groupCount() {
    return parentPattern.capturingGroupCount - 1;
  }

  /**
   * Attempts to match the entire region against the pattern.
   *
   * <p> If the match succeeds then more information can be obtained via the
   * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
   *
   * @return <tt>true</tt> if, and only if, the entire region sequence matches this matcher's
   * pattern
   */
  public boolean matches() {
    return match(from, ENDANCHOR);
  }

  /**
   * Attempts to find the next subsequence of the input sequence that matches
   * the pattern.
   *
   * <p> This method starts at the beginning of this matcher's region, or, if
   * a previous invocation of the method was successful and the matcher has
   * not since been reset, at the first character not matched by the previous
   * match.
   *
   * <p> If the match succeeds then more information can be obtained via the
   * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
   *
   * @return <tt>true</tt> if, and only if, a subsequence of the input sequence matches this
   * matcher's pattern
   */
  public boolean find() {
    int nextSearchIndex = last;
    if (nextSearchIndex == first) {
      nextSearchIndex++;
    }

    // If next search starts before region, start it at region
    if (nextSearchIndex < from) {
      nextSearchIndex = from;
    }

    // If next search starts beyond region then it fails
    if (nextSearchIndex > to) {
      for (int i = 0; i < groups.length; i++) {
        groups[i] = -1;
      }
      return false;
    }
    return search(nextSearchIndex);
  }

  /**
   * Resets this matcher and then attempts to find the next subsequence of
   * the input sequence that matches the pattern, starting at the specified
   * index.
   *
   * <p> If the match succeeds then more information can be obtained via the
   * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods, and subsequent
   * invocations of the {@link #find()} method will start at the first
   * character not matched by this match.  </p>
   *
   * @param start the index to start searching for a match
   * @return <tt>true</tt> if, and only if, a subsequence of the input sequence starting at the
   * given index matches this matcher's pattern
   * @throws IndexOutOfBoundsException If start is less than zero or if start is greater than the
   * length of the input sequence.
   */
  public boolean find(int start) {
    int limit = getTextLength();
    if ((start < 0) || (start > limit)) {
      throw new IndexOutOfBoundsException("Illegal start index");
    }
    reset();
    return search(start);
  }

  /**
   * Attempts to match the input sequence, starting at the beginning of the
   * region, against the pattern.
   *
   * <p> Like the {@link #matches matches} method, this method always starts
   * at the beginning of the region; unlike that method, it does not
   * require that the entire region be matched.
   *
   * <p> If the match succeeds then more information can be obtained via the
   * <tt>start</tt>, <tt>end</tt>, and <tt>group</tt> methods.  </p>
   *
   * @return <tt>true</tt> if, and only if, a prefix of the input sequence matches this matcher's
   * pattern
   */
  public boolean lookingAt() {
    return match(from, NOANCHOR);
  }

  /**
   * Returns a literal replacement <code>String</code> for the specified
   * <code>String</code>.
   *
   * This method produces a <code>String</code> that will work
   * as a literal replacement <code>s</code> in the
   * <code>appendReplacement</code> method of the {@link Matcher} class.
   * The <code>String</code> produced will match the sequence of characters
   * in <code>s</code> treated as a literal sequence. Slashes ('\') and
   * dollar signs ('$') will be given no special meaning.
   *
   * @param s The string to be literalized
   * @return A literal string replacement
   * @since 1.5
   */
  public static String quoteReplacement(String s) {
    if ((s.indexOf('\\') == -1) && (s.indexOf('$') == -1)) {
      return s;
    }
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < s.length(); i++) {
      char c = s.charAt(i);
      if (c == '\\' || c == '$') {
        sb.append('\\');
      }
      sb.append(c);
    }
    return sb.toString();
  }

  /**
   * Implements a non-terminal append-and-replace step.
   *
   * <p> This method performs the following actions: </p>
   *
   * <ol>
   *
   * <li><p> It reads characters from the input sequence, starting at the
   * append position, and appends them to the given string buffer.  It
   * stops after reading the last character preceding the previous match,
   * that is, the character at index {@link
   * #start()}&nbsp;<tt>-</tt>&nbsp;<tt>1</tt>.  </p></li>
   *
   * <li><p> It appends the given replacement string to the string buffer.
   * </p></li>
   *
   * <li><p> It sets the append position of this matcher to the index of
   * the last character matched, plus one, that is, to {@link #end()}.
   * </p></li>
   *
   * </ol>
   *
   * <p> The replacement string may contain references to subsequences
   * captured during the previous match: Each occurrence of
   * <tt>${</tt><i>name</i><tt>}</tt> or <tt>$</tt><i>g</i>
   * will be replaced by the result of evaluating the corresponding
   * {@link #group(String) group(name)} or {@link #group(int) group(g)}
   * respectively. For  <tt>$</tt><i>g</i>,
   * the first number after the <tt>$</tt> is always treated as part of
   * the group reference. Subsequent numbers are incorporated into g if
   * they would form a legal group reference. Only the numerals '0'
   * through '9' are considered as potential components of the group
   * reference. If the second group matched the string <tt>"foo"</tt>, for
   * example, then passing the replacement string <tt>"$2bar"</tt> would
   * cause <tt>"foobar"</tt> to be appended to the string buffer. A dollar
   * sign (<tt>$</tt>) may be included as a literal in the replacement
   * string by preceding it with a backslash (<tt>\$</tt>).
   *
   * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
   * the replacement string may cause the results to be different than if it
   * were being treated as a literal replacement string. Dollar signs may be
   * treated as references to captured subsequences as described above, and
   * backslashes are used to escape literal characters in the replacement
   * string.
   *
   * <p> This method is intended to be used in a loop together with the
   * {@link #appendTail appendTail} and {@link #find find} methods.  The
   * following code, for example, writes <tt>one dog two dogs in the
   * yard</tt> to the standard-output stream: </p>
   *
   * <blockquote><pre>
   * Pattern p = Pattern.compile("cat");
   * Matcher m = p.matcher("one cat two cats in the yard");
   * StringBuffer sb = new StringBuffer();
   * while (m.find()) {
   *     m.appendReplacement(sb, "dog");
   * }
   * m.appendTail(sb);
   * System.out.println(sb.toString());</pre></blockquote>
   *
   * @param sb The target string buffer
   * @param replacement The replacement string
   * @return This matcher
   * @throws IllegalStateException If no match has yet been attempted, or if the previous match
   * operation failed
   * @throws IllegalArgumentException If the replacement string refers to a named-capturing group
   * that does not exist in the pattern
   * @throws IndexOutOfBoundsException If the replacement string refers to a capturing group that
   * does not exist in the pattern
   */
  public Matcher appendReplacement(StringBuffer sb, String replacement) {

    // If no match, return error
    if (first < 0) {
      throw new IllegalStateException("No match available");
    }

    // Process substitution string to replace group references with groups
    int cursor = 0;
    StringBuilder result = new StringBuilder();

    while (cursor < replacement.length()) {
      char nextChar = replacement.charAt(cursor);
      if (nextChar == '\\') {
        cursor++;
        if (cursor == replacement.length()) {
          throw new IllegalArgumentException(
              "character to be escaped is missing");
        }
        nextChar = replacement.charAt(cursor);
        result.append(nextChar);
        cursor++;
      } else if (nextChar == '$') {
        // Skip past $
        cursor++;
        // Throw IAE if this "$" is the last character in replacement
        if (cursor == replacement.length()) {
          throw new IllegalArgumentException(
              "Illegal group reference: group index is missing");
        }
        nextChar = replacement.charAt(cursor);
        int refNum = -1;
        if (nextChar == '{') {
          cursor++;
          StringBuilder gsb = new StringBuilder();
          while (cursor < replacement.length()) {
            nextChar = replacement.charAt(cursor);
            if (ASCII.isLower(nextChar) ||
                ASCII.isUpper(nextChar) ||
                ASCII.isDigit(nextChar)) {
              gsb.append(nextChar);
              cursor++;
            } else {
              break;
            }
          }
          if (gsb.length() == 0) {
            throw new IllegalArgumentException(
                "named capturing group has 0 length name");
          }
          if (nextChar != '}') {
            throw new IllegalArgumentException(
                "named capturing group is missing trailing '}'");
          }
          String gname = gsb.toString();
          if (ASCII.isDigit(gname.charAt(0))) {
            throw new IllegalArgumentException(
                "capturing group name {" + gname +
                    "} starts with digit character");
          }
          if (!parentPattern.namedGroups().containsKey(gname)) {
            throw new IllegalArgumentException(
                "No group with name {" + gname + "}");
          }
          refNum = parentPattern.namedGroups().get(gname);
          cursor++;
        } else {
          // The first number is always a group
          refNum = (int) nextChar - '0';
          if ((refNum < 0) || (refNum > 9)) {
            throw new IllegalArgumentException(
                "Illegal group reference");
          }
          cursor++;
          // Capture the largest legal group string
          boolean done = false;
          while (!done) {
            if (cursor >= replacement.length()) {
              break;
            }
            int nextDigit = replacement.charAt(cursor) - '0';
            if ((nextDigit < 0) || (nextDigit > 9)) { // not a number
              break;
            }
            int newRefNum = (refNum * 10) + nextDigit;
            if (groupCount() < newRefNum) {
              done = true;
            } else {
              refNum = newRefNum;
              cursor++;
            }
          }
        }
        // Append group
        if (start(refNum) != -1 && end(refNum) != -1) {
          result.append(text, start(refNum), end(refNum));
        }
      } else {
        result.append(nextChar);
        cursor++;
      }
    }
    // Append the intervening text
    sb.append(text, lastAppendPosition, first);
    // Append the match substitution
    sb.append(result);

    lastAppendPosition = last;
    return this;
  }

  /**
   * Implements a terminal append-and-replace step.
   *
   * <p> This method reads characters from the input sequence, starting at
   * the append position, and appends them to the given string buffer.  It is
   * intended to be invoked after one or more invocations of the {@link
   * #appendReplacement appendReplacement} method in order to copy the
   * remainder of the input sequence.  </p>
   *
   * @param sb The target string buffer
   * @return The target string buffer
   */
  public StringBuffer appendTail(StringBuffer sb) {
    sb.append(text, lastAppendPosition, getTextLength());
    return sb;
  }

  /**
   * Replaces every subsequence of the input sequence that matches the
   * pattern with the given replacement string.
   *
   * <p> This method first resets this matcher.  It then scans the input
   * sequence looking for matches of the pattern.  Characters that are not
   * part of any match are appended directly to the result string; each match
   * is replaced in the result by the replacement string.  The replacement
   * string may contain references to captured subsequences as in the {@link
   * #appendReplacement appendReplacement} method.
   *
   * <p> Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
   * the replacement string may cause the results to be different than if it
   * were being treated as a literal replacement string. Dollar signs may be
   * treated as references to captured subsequences as described above, and
   * backslashes are used to escape literal characters in the replacement
   * string.
   *
   * <p> Given the regular expression <tt>a*b</tt>, the input
   * <tt>"aabfooaabfooabfoob"</tt>, and the replacement string
   * <tt>"-"</tt>, an invocation of this method on a matcher for that
   * expression would yield the string <tt>"-foo-foo-foo-"</tt>.
   *
   * <p> Invoking this method changes this matcher's state.  If the matcher
   * is to be used in further matching operations then it should first be
   * reset.  </p>
   *
   * @param replacement The replacement string
   * @return The string constructed by replacing each matching subsequence by the replacement
   * string, substituting captured subsequences as needed
   */
  public String replaceAll(String replacement) {
    reset();
    boolean result = find();
    if (result) {
      StringBuffer sb = new StringBuffer();
      do {
        appendReplacement(sb, replacement);
        result = find();
      } while (result);
      appendTail(sb);
      return sb.toString();
    }
    return text.toString();
  }

  /**
   * Replaces the first subsequence of the input sequence that matches the
   * pattern with the given replacement string.
   *
   * <p> This method first resets this matcher.  It then scans the input
   * sequence looking for a match of the pattern.  Characters that are not
   * part of the match are appended directly to the result string; the match
   * is replaced in the result by the replacement string.  The replacement
   * string may contain references to captured subsequences as in the {@link
   * #appendReplacement appendReplacement} method.
   *
   * <p>Note that backslashes (<tt>\</tt>) and dollar signs (<tt>$</tt>) in
   * the replacement string may cause the results to be different than if it
   * were being treated as a literal replacement string. Dollar signs may be
   * treated as references to captured subsequences as described above, and
   * backslashes are used to escape literal characters in the replacement
   * string.
   *
   * <p> Given the regular expression <tt>dog</tt>, the input
   * <tt>"zzzdogzzzdogzzz"</tt>, and the replacement string
   * <tt>"cat"</tt>, an invocation of this method on a matcher for that
   * expression would yield the string <tt>"zzzcatzzzdogzzz"</tt>.  </p>
   *
   * <p> Invoking this method changes this matcher's state.  If the matcher
   * is to be used in further matching operations then it should first be
   * reset.  </p>
   *
   * @param replacement The replacement string
   * @return The string constructed by replacing the first matching subsequence by the replacement
   * string, substituting captured subsequences as needed
   */
  public String replaceFirst(String replacement) {
    if (replacement == null) {
      throw new NullPointerException("replacement");
    }
    reset();
    if (!find()) {
      return text.toString();
    }
    StringBuffer sb = new StringBuffer();
    appendReplacement(sb, replacement);
    appendTail(sb);
    return sb.toString();
  }

  /**
   * Sets the limits of this matcher's region. The region is the part of the
   * input sequence that will be searched to find a match. Invoking this
   * method resets the matcher, and then sets the region to start at the
   * index specified by the <code>start</code> parameter and end at the
   * index specified by the <code>end</code> parameter.
   *
   * <p>Depending on the transparency and anchoring being used (see
   * {@link #useTransparentBounds useTransparentBounds} and
   * {@link #useAnchoringBounds useAnchoringBounds}), certain constructs such
   * as anchors may behave differently at or around the boundaries of the
   * region.
   *
   * @param start The index to start searching at (inclusive)
   * @param end The index to end searching at (exclusive)
   * @return this matcher
   * @throws IndexOutOfBoundsException If start or end is less than zero, if start is greater than
   * the length of the input sequence, if end is greater than the length of the input sequence, or
   * if start is greater than end.
   * @since 1.5
   */
  public Matcher region(int start, int end) {
    if ((start < 0) || (start > getTextLength())) {
      throw new IndexOutOfBoundsException("start");
    }
    if ((end < 0) || (end > getTextLength())) {
      throw new IndexOutOfBoundsException("end");
    }
    if (start > end) {
      throw new IndexOutOfBoundsException("start > end");
    }
    reset();
    from = start;
    to = end;
    return this;
  }

  /**
   * Reports the start index of this matcher's region. The
   * searches this matcher conducts are limited to finding matches
   * within {@link #regionStart regionStart} (inclusive) and
   * {@link #regionEnd regionEnd} (exclusive).
   *
   * @return The starting point of this matcher's region
   * @since 1.5
   */
  public int regionStart() {
    return from;
  }

  /**
   * Reports the end index (exclusive) of this matcher's region.
   * The searches this matcher conducts are limited to finding matches
   * within {@link #regionStart regionStart} (inclusive) and
   * {@link #regionEnd regionEnd} (exclusive).
   *
   * @return the ending point of this matcher's region
   * @since 1.5
   */
  public int regionEnd() {
    return to;
  }

  /**
   * Queries the transparency of region bounds for this matcher.
   *
   * <p> This method returns <tt>true</tt> if this matcher uses
   * <i>transparent</i> bounds, <tt>false</tt> if it uses <i>opaque</i>
   * bounds.
   *
   * <p> See {@link #useTransparentBounds useTransparentBounds} for a
   * description of transparent and opaque bounds.
   *
   * <p> By default, a matcher uses opaque region boundaries.
   *
   * @return <tt>true</tt> iff this matcher is using transparent bounds, <tt>false</tt> otherwise.
   * @see java.util.regex.Matcher#useTransparentBounds(boolean)
   * @since 1.5
   */
  public boolean hasTransparentBounds() {
    return transparentBounds;
  }

  /**
   * Sets the transparency of region bounds for this matcher.
   *
   * <p> Invoking this method with an argument of <tt>true</tt> will set this
   * matcher to use <i>transparent</i> bounds. If the boolean
   * argument is <tt>false</tt>, then <i>opaque</i> bounds will be used.
   *
   * <p> Using transparent bounds, the boundaries of this
   * matcher's region are transparent to lookahead, lookbehind,
   * and boundary matching constructs. Those constructs can see beyond the
   * boundaries of the region to see if a match is appropriate.
   *
   * <p> Using opaque bounds, the boundaries of this matcher's
   * region are opaque to lookahead, lookbehind, and boundary matching
   * constructs that may try to see beyond them. Those constructs cannot
   * look past the boundaries so they will fail to match anything outside
   * of the region.
   *
   * <p> By default, a matcher uses opaque bounds.
   *
   * @param b a boolean indicating whether to use opaque or transparent regions
   * @return this matcher
   * @see java.util.regex.Matcher#hasTransparentBounds
   * @since 1.5
   */
  public Matcher useTransparentBounds(boolean b) {
    transparentBounds = b;
    return this;
  }

  /**
   * Queries the anchoring of region bounds for this matcher.
   *
   * <p> This method returns <tt>true</tt> if this matcher uses
   * <i>anchoring</i> bounds, <tt>false</tt> otherwise.
   *
   * <p> See {@link #useAnchoringBounds useAnchoringBounds} for a
   * description of anchoring bounds.
   *
   * <p> By default, a matcher uses anchoring region boundaries.
   *
   * @return <tt>true</tt> iff this matcher is using anchoring bounds, <tt>false</tt> otherwise.
   * @see java.util.regex.Matcher#useAnchoringBounds(boolean)
   * @since 1.5
   */
  public boolean hasAnchoringBounds() {
    return anchoringBounds;
  }

  /**
   * Sets the anchoring of region bounds for this matcher.
   *
   * <p> Invoking this method with an argument of <tt>true</tt> will set this
   * matcher to use <i>anchoring</i> bounds. If the boolean
   * argument is <tt>false</tt>, then <i>non-anchoring</i> bounds will be
   * used.
   *
   * <p> Using anchoring bounds, the boundaries of this
   * matcher's region match anchors such as ^ and $.
   *
   * <p> Without anchoring bounds, the boundaries of this
   * matcher's region will not match anchors such as ^ and $.
   *
   * <p> By default, a matcher uses anchoring region boundaries.
   *
   * @param b a boolean indicating whether or not to use anchoring bounds.
   * @return this matcher
   * @see java.util.regex.Matcher#hasAnchoringBounds
   * @since 1.5
   */
  public Matcher useAnchoringBounds(boolean b) {
    anchoringBounds = b;
    return this;
  }

  /**
   * <p>Returns the string representation of this matcher. The
   * string representation of a <code>Matcher</code> contains information
   * that may be useful for debugging. The exact format is unspecified.
   *
   * @return The string representation of this matcher
   * @since 1.5
   */
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("java.util.regex.Matcher");
    sb.append("[pattern=" + pattern());
    sb.append(" region=");
    sb.append(regionStart() + "," + regionEnd());
    sb.append(" lastmatch=");
    if ((first >= 0) && (group() != null)) {
      sb.append(group());
    }
    sb.append("]");
    return sb.toString();
  }

  /**
   * <p>Returns true if the end of input was hit by the search engine in
   * the last match operation performed by this matcher.
   *
   * <p>When this method returns true, then it is possible that more input
   * would have changed the result of the last search.
   *
   * @return true iff the end of input was hit in the last match; false otherwise
   * @since 1.5
   */
  public boolean hitEnd() {
    return hitEnd;
  }

  /**
   * <p>Returns true if more input could change a positive match into a
   * negative one.
   *
   * <p>If this method returns true, and a match was found, then more
   * input could cause the match to be lost. If this method returns false
   * and a match was found, then more input might change the match but the
   * match won't be lost. If a match was not found, then requireEnd has no
   * meaning.
   *
   * @return true iff more input could change a positive match into a negative one.
   * @since 1.5
   */
  public boolean requireEnd() {
    return requireEnd;
  }

  /**
   * Initiates a search to find a Pattern within the given bounds.
   * The groups are filled with default values and the match of the root
   * of the state machine is called. The state machine will hold the state
   * of the match as it proceeds in this matcher.
   *
   * Matcher.from is not set here, because it is the "hard" boundary
   * of the start of the search which anchors will set to. The from param
   * is the "soft" boundary of the start of the search, meaning that the
   * regex tries to match at that index but ^ won't match there. Subsequent
   * calls to the search methods start at a new "soft" boundary which is
   * the end of the previous match.
   */
  boolean search(int from) {
    this.hitEnd = false;
    this.requireEnd = false;
    from = from < 0 ? 0 : from;
    this.first = from;
    this.oldLast = oldLast < 0 ? from : oldLast;
    for (int i = 0; i < groups.length; i++) {
      groups[i] = -1;
    }
    acceptMode = NOANCHOR;
    boolean result = parentPattern.root.match(this, from, text);
    if (!result) {
      this.first = -1;
    }
    this.oldLast = this.last;
    return result;
  }

  /**
   * Initiates a search for an anchored match to a Pattern within the given
   * bounds. The groups are filled with default values and the match of the
   * root of the state machine is called. The state machine will hold the
   * state of the match as it proceeds in this matcher.
   */
  boolean match(int from, int anchor) {
    this.hitEnd = false;
    this.requireEnd = false;
    from = from < 0 ? 0 : from;
    this.first = from;
    this.oldLast = oldLast < 0 ? from : oldLast;
    for (int i = 0; i < groups.length; i++) {
      groups[i] = -1;
    }
    acceptMode = anchor;
    boolean result = parentPattern.matchRoot.match(this, from, text);
    if (!result) {
      this.first = -1;
    }
    this.oldLast = this.last;
    return result;
  }

  /**
   * Returns the end index of the text.
   *
   * @return the index after the last character in the text
   */
  int getTextLength() {
    return text.length();
  }

  /**
   * Generates a String from this Matcher's input in the specified range.
   *
   * @param beginIndex the beginning index, inclusive
   * @param endIndex the ending index, exclusive
   * @return A String generated from this Matcher's input
   */
  CharSequence getSubSequence(int beginIndex, int endIndex) {
    return text.subSequence(beginIndex, endIndex);
  }

  /**
   * Returns this Matcher's input character at index i.
   *
   * @return A char from the specified index
   */
  char charAt(int i) {
    return text.charAt(i);
  }

  /**
   * Returns the group index of the matched capturing group.
   *
   * @return the index of the named-capturing group
   */
  int getMatchedGroupIndex(String name) {
    Objects.requireNonNull(name, "Group name");
    if (first < 0) {
      throw new IllegalStateException("No match found");
    }
    if (!parentPattern.namedGroups().containsKey(name)) {
      throw new IllegalArgumentException("No group with name <" + name + ">");
    }
    return parentPattern.namedGroups().get(name);
  }
}
